<template>
  <div class="camera_outer">
    <video id="videoCamera" :width="videoWidth" :height="videoHeight" autoplay></video>
    <canvas style="display:none;" id="canvasCamera" :width="videoWidth" :height="videoHeight"></canvas>
    <div v-if="imgSrc" class="img_bg_camera">
      <img :src="imgSrc" alt="" class="tx_img">
    </div>
    <el-button @click="getCompetence()">打开摄像头</el-button>
    <el-button @click="stopNavigator()">关闭摄像头</el-button>
    <el-button @click="setImage()">拍照</el-button>
  </div>
</template>
<script>
export default {
  data() {
    return {
      videoWidth: 800,
      videoHeight: 300,
      imgSrc: '',
      thisCancas: null,
      thisContext: null,
      thisVideo: null,
    };
  },
  created() {
  },
  methods: {
    getCompetence() {
      var _this = this
      this.thisCancas = document.getElementById('canvasCamera')
      this.thisContext = this.thisCancas.getContext('2d')
      this.thisVideo = document.getElementById('videoCamera')
      // 旧版本浏览器可能根本不支持mediaDevices，我们首先设置一个空对象
      if (navigator.mediaDevices === undefined) {
        navigator.mediaDevices = {}
      }
      // 一些浏览器实现了部分mediaDevices，我们不能只分配一个对象
      // 使用getUserMedia，因为它会覆盖现有的属性。
      // 这里，如果缺少getUserMedia属性，就添加它。
      if (navigator.mediaDevices.getUserMedia === undefined) {
        navigator.mediaDevices.getUserMedia = function (constraints) {
          // 首先获取现存的getUserMedia(如果存在)
          var getUserMedia = navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.getUserMedia
          // 有些浏览器不支持，会返回错误信息
          // 保持接口一致
          if (!getUserMedia) {
            return Promise.reject(new Error('getUserMedia is not implemented in this browser'))
          }
          // 否则，使用Promise将调用包装到旧的navigator.getUserMedia
          return new Promise(function (resolve, reject) {
            getUserMedia.call(navigator, constraints, resolve, reject)
          })
        }
      }
      var constraints = {audio: false, video: {width: this.videoWidth, height: this.videoHeight, transform: 'scaleX(-1)'}}
      navigator.mediaDevices.getUserMedia(constraints).then(function (stream) {
        // 旧的浏览器可能没有srcObject
        if ('srcObject' in _this.thisVideo) {
          _this.thisVideo.srcObject = stream
        } else {
          // 避免在新的浏览器中使用它，因为它正在被弃用。
          _this.thisVideo.src = window.URL.createObjectURL(stream)
        }
        _this.thisVideo.onloadedmetadata = function (e) {
          _this.thisVideo.play()
          console.info(e);
        }
      }).catch(err => {
        console.log(err)
      })
    },
    //  绘制图片（拍照功能）
    setImage() {
      var _this = this
      // 点击，canvas画图
      _this.thisContext.drawImage(_this.thisVideo, 0, 0, _this.videoWidth, _this.videoHeight)
      // 获取图片base64链接
      var image = this.thisCancas.toDataURL('image/png')
      _this.imgSrc = image
      this.$emit('refreshDataList', this.imgSrc)
    },
    // base64转文件
    dataURLtoFile(dataurl, filename) {
      var arr = dataurl.split(',')
      var mime = arr[0].match(/:(.*?);/)[1]
      var bstr = atob(arr[1])
      var n = bstr.length
      var u8arr = new Uint8Array(n)
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n)
      }
      return new File([u8arr], filename, {type: mime})
    },
    // 关闭摄像头
    stopNavigator() {
      this.thisVideo.srcObject.getTracks()[0].stop()
    }
  }
};
</script>
<style scoped>
.dashboard-container {
  width: 100%;
  height: 100%;
  color: #fff;
}

.tx_img {
  max-width: 100%;
}
</style>
